In recent years, liquid crystal displays attract attentions as image display devices. Liquid crystal displays are applied to portable electronic organizers, information terminals etc., and for example, they are used as input devices of portable electronic organizers, information terminals etc. When a liquid crystal display device is used as an input device, a structure that a transparent touch panel is placed on the liquid crystal display device is adopted. In particular, a resistance film type touch panel is generally used in view of price etc.
As the resistance film type touch panel, those having a structure that a transparent conductive film and glass having a transparent conductive film are disposed so that they are separated with an appropriate gap are generally used. When the transparent conductive film is pushed down with a finger or pen, it touches the glass having a transparent conductive film, and both are electrically connected. Pushing down of the film is thereby electrically detected.
As the transparent conductive film, a film comprising a base material film such as a plastic film and a transparent conductive film such as indium tin oxide (henceforth referred to as “ITO”) formed on the lower surface of the base material film (surface facing glass having a transparent conductive film) is generally used. As the base material film, a transparent hard coat film formed by providing a transparent hard coat layer on a surface of a transparent polymer film is used. Use of a transparent hard coat film as the base material film of the transparent conductive film can improve durability of the transparent conductive film.
Under the environment where input devices such as portable electronic organizers and information terminals are used, three-band fluorescent lamps are frequently used as illumination. This is because three-band fluorescent lamps have characteristics that they show strong luminescence intensities for specific three kinds of wavelengths and can clearly visualize objects.
However, as described in Patent document 1, currently used transparent hard coat films incorporated into touch panels or the like may generate interference patterns due to uneven thickness of the transparent hard coat films, and have a problem that interference patterns becomes conspicuous especially in an environment where three-band fluorescent lamps are used for illumination. Although such interference patterns can be eliminated by using a transparent polymer film and a transparent hard coat film having the same refractive index as those constituting the transparent hard coated film, it is difficult to control the refractive index of the transparent hard coat film with maintaining the hard coat properties thereof. It is also possible to make interference patterns inconspicuous by making surface of the transparent hard coat film uneven by incorporating a matting agent into it. However, such incorporation of matting agent degrades sharpness of images observed through the transparent hard coat film (image sharpness). Patent document 1 discloses suppression of interference patterns by adjustment of hue and saturation of the transparent hard coat film.
Patent document 2 discloses a double-layer structure of an anti-reflection layer provided on a hard coat film for suppressing generation of interference patterns in the anti-reflection layer due to uneven thickness of the anti-reflection layer, wherein the anti-reflection layer consists of a high refractive index layer and low refractive index layer having refractive indexes in predetermined ranges.    Patent document 1: Japanese Patent Unexamined Publication (KOKAI) No. 2003-334891 (Background Art)    Patent document 2: Japanese Patent Unexamined Publication No. 2005-257840 (Background Art)